What does the first law of reflection state?
The First Law of reflection States that the angle made by the incident light ray with the normal to the surface at the point of incidence is equal to angle made by the reflected light ray with the normal.
The following figures are examples of this law under different circumstances:
1) A flat Mirror
One note of caution though always take the Normal at the point of incidence, telling this is trivial for plane mirrors as normal is always the same but in curved mirrors the normal changes from point to point so always remember to take the normal at the point of incidence.
Nice applet on this website: http://www.physicsclassroom.com/mmedia/optics/lr.cfm